The present invention relates to electronic switching devices for switching of electromechanical loads, and particularly to addressable electronic switching devices.
Control systems, industrial equipment and computer pripherals commonly utilize electromechanical devices such as solenoids or motors which are selectively energized under control of a central computer or controller. Different actuators receive power from individual power switching circuits conventionally connected to separate output ports of the computer or controller. Electronic cash registers and transaction terminals provide examples of systems having a number of pripherals controlled by a computer. Normally the cash drawers associated with such systems are spring-loaded and are opened by energizing a solenoid to release a latch. A complete cash register or terminal typically includes one or more cash drawers, often located remote from an associated terminal, as well as a number of other peripheral devices such as receipt printers, displays, bar code readers. electronic scales, and in some cases credit card validators and coupon dispensers. Existing systems generally require a separate input/output port for each cash drawer or other peripheral device, which introduces considerable expense in comparison to the cost of a cash drawer or peripheral device.
Peripheral devices are sometimes connected in parallel with one input/output port, commonly employing Y-cable splices. Such splices are not only unduly cumbersome but they place unwanted restrictions on the baud rate and length of data cable due to the necessarily limited drive capability of any host computer terminal. The addressing scheme of the present invention permits connection of multiple switching devices to a single port without adversely affecting data transmission.
Any cash register system further has associated with it considerations of security. Attempts have been made to increase security, from completely mechanical locks to a solenoid-controlled latch mechanism which is supplied with power to actuate the solenoid only after completion of an authorized transaction. Electrical key systems have employed keys with shorting contacts for placement into an electrically conductive keyway to cause the solenoid action necessary to unlock the drawer, as well as special keys having resistors or capacitors of predetermined values which can be detected by a sensing circuit. However, unauthorized access to any of these systems has proven to be possible without much difficulty. In contrast, a cash drawer utilizing the teachings of the present invention opens only when addressed with a specific access code.